A .NET wrapper on the ImageMagick library (http://imagemagick.org).
Minimalist Game Framework for Xna. A very simple, yet more flexible alternative to Xna's Game framework.
Onyx CE (Content Editor) is designed to be an extensible toolkit for creating content (scripts, maps, tilesets, and sprites) for 2D games. It intends to support the formats for the Game Creation Engines ika, Verge, and Sphere.
A DirectX based graphics/physics engine
As of now, an independently developed graphics/physics engine for use with DirectX9/DirectX11 and C++. I'm only working on this during my free time, so it will not be updated too often unless I have something major to add to it. Outside insight would be appreciated.